Exhaust device for small sized boat engine

ABSTRACT

A small watercraft embodying an improved exhaust system that is substantially completely watercooled by a cooling jacket. The exhaust system includes an elastic joint that is also completely surrounded by the cooling jacket so as to insure adequate cooling under all running conditions. A damming arrangement is incorporated so as to insure that all of the exhaust portions being cooled will be completely encircled with cooling water even when low amounts of water are being circulated and a drain system is also provided so as to insure that the cooling jackets will be drained when the watercraft is removed from a body of water.

This is a division of U.S. patent application Ser. No. 638,824, filedJan. 8, 1991, now abandoned; which was a division of U.S. patentapplication Ser. No. 411,033, filed Sep. 22, 1989, now U.S. Pat. No.4,989,409.

BACKGROUND OF THE INVENTION

This invention relates to an exhaust device for a small sized boatengine and more particularly to an improved arrangement for dischargingand cooling the exhaust gases from an internal combustion engine,particularly when applied in a marine application.

In conjunction with the application of internal combustion engines forpowering marine craft, it is a common practice to discharge at least aportion of the cooling water from the engine cooling jacket into theexhaust system so as to cool the exhaust and silence it. When this isdone, it is possible to employ elastic joints in the exhaust system soas to permit some relative movement, absorb vibrations and avoid againstundue stresses in the exhaust system. However, it has been found thatthe amount of cooling water discharged into the exhaust manifold may notbe sufficient under all running conditions to cool the elastic jointsadequately. If not cooled adequately, the joint can deteriorate with agewith eventual failure.

It has, therefore, been proposed to provide a further arrangement forcooling the elastic joints. However, the type of cooling systemspreviously proposed have not truly been effective in providing adequatecooling for all parts of the elastic joint.

It is, therefore, a principle object of this invention to provide animproved arrangement for cooling an elastic joint in an internalcombustion engine exhaust system.

It is a further object of this invention to provide an improved exhaustsystem for a small watercraft wherein the elastic joints in the systemare adequately cooled under all conditions.

SUMMARY OF THE INVENTION

This invention is adapted to be embodied in an exhaust system for aninternal combustion engine that is comprised of a first inner pipehaving an outlet end and a second inner pipe having an inlet end spacedfrom the outlet end of the first inner pipe. A first outer pipeencircles at least in part the first inner pipe and a second pipeencircles at least in part the second inner pipe. The outer pipes havespaced apart ends. An inner elastic joint interconnects the outlet andinlet ends of the inner pipes for exhaust gas flow therebetween. Anouter elastic joint connects the ends of the outer pipes to define acooling jacket around the first elastic joint. Means are provided foradmitting cooling water to the cooling jacket for cooling the elasticjoint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a small watercraft constructed inaccordance with an embodiment of the invention.

FIG. 2 is a top plan view, with portions broken away and other portionsshown in section, of the drive arrangement for the small watercraft.

FIG. 3 is an enlarged cross sectional view taken through the exhaustsystem of the engine generally along the line 3--3 of FIG. 4.

FIG. 4 is a cross sectional view taken generally along the line 4--4 ofFIG. 3 and shows the engine and its exhaust system.

FIG. 5 is a cross sectional view taken along the line 5--5 of FIG. 3.

FIG. 6 is a cross sectional view taken along the line 6--6 of FIG. 3.

FIG. 7 is a cross sectional view taken along the line 7--7 of FIG. 3.

FIG. 8 is a top plan view of the engine.

FIG. 9 is a cross sectional view taken along the line 9--9 of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Referring first to FIGS. 1 and 2, a small watercraft is indicatedgenerally by the reference numeral 11 and is depicted as a typicalenvironment in which the invention may be employed. The small watercraft11 is provided with an engine compartment in which an internalcombustion engine 12 is positioned. Although the invention is capable ofuse with a wide variety of types of engines, in the illustratedembodiment, the engine 12 of the two cylinder in-line type and operateson the two-stroke crankcase compression principle.

As may be seen in FIG. 4, the engine 12 is comprised of a cylinder block13 in which a pair of cylinder bores (only one of which appears in thisfigure) are formed. Pistons 14 reciprocate in these cylinder bores andare connected by means of connecting rods (not shown) to a crankshaft 15of the engine. The crankshaft 15 is coupled by means of a coupling 16 toa driveshaft 17 of a jet propulsion unit indicated generally by thereference numeral 18.

The jet propulsion unit 18 is positioned within a recess or tunnel 19formed centrally and at the rear of the hull of the watercraft 11. Thejet propulsion unit 18 includes a downwardly facing water inlet 21 intowhich water is drawn past by an impellers 22 and is discharged paststraightening vanes 23. The water is then discharged through a steeringnozzle 24 that is steered by a means of a handlebar assembly 25positioned immediately forward of a rider's seat 26 on a mast 27. Arider, shown in phantom in FIG. 1, is adapted to sit upon the seat 26 ina straddle fashion for operating the watercraft in a well known manner.

Referring again to FIG. 4, the engine 12 is provided with an inductionsystem that includes an air intake device 28 which delivers air to oneor more carburetors 29. The carburetors 29 in turn deliver a fuel aircharge to the crankcase chambers of the engine through an intakemanifold 31. This charge is then transferred to the combustion chamberthrough respective scavenge passages 32, as is well known in this art.

A cylinder head 33 is affixed to the cylinder block 13 in a known mannerand mounts individual spark plugs 34 for each of the cylinders of theengine. The spark plugs 34 are fired by means of a suitable ignitionsystem depicted schematically in FIG. 2 at 35.

It should be noted that the spark plugs 34 are provided with combinedterminals and protective boots 36 which encircle the exposed portion ofthe spark plug 34 and which have a skirt portion 37 that extends into arecess in the cylinder head cover 38 so as to provide a good water tightseal.

The exhaust gases from the individual combustion chambers are dischargedthrough respective exhaust ports 39 that extend through the side of thecylinder block 13 and which cooperate with an exhaust manifold andexhaust system of a type to be described.

The engine 12 is also provided with a liquid cooling system thatincludes a cooling jacket 41 that encircles the components of the engineto be cooled and which is formed in the cylinder block 13 and cylinderhead 33. Coolant is drawn for the engine cooling system from the body ofwater in which the watercraft is operating in a suitable manner anddischarged in a manner which will be described.

The engine 12 is mounted within the hull of the watercraft by means of aplurality of resilient engine mounts 42 (FIG. 4).

The exhaust system of the engine will now be described by primaryreference to the remaining FIGS. (3 through 8) although the exhaustsystem is also shown partially schematically in FIG. 2. There isprovided an exhaust manifold that is comprised of a generallycylindrical expansion chamber portion 43 that runs longitudinally alongone side of the engine and which is closed at one end by means of acover plate 44. The expansion chamber 43 communicates with theindividual exhaust ports 39 of the cylinder block 33 through respectiverunner portions 45.

In accordance with the invention, the cylindrical portion 43 is furtherenclosed by means of a cylindrical outer member 46 which defines ajacket or cooling chamber 47 around the periphery of the manifoldportion 43 and also around the individual runners 45. Coolant isdelivered to the cooling jacket 47 from the jet propulsion unit 18through a flexible conduit 49 at the lowest portion of the coolingjacket 47 as clearly shown in FIG. 3. The coolant delivered to thecooling jacket 47 is then transferred through restricted ports 48 to thecooling jacket 41 of the engine 12. The size of the ports 48 willdetermine how much water is delivered from the cooling jacket 47 to theengine cooling jacket 41.

The first expansion chamber formed by the manifold portion 43communicates with a second expansion chamber, indicated by the referencenumeral 51 through a U-shaped connecting joint 52 constructed inaccordance with an embodiment of the invention. This U-shaped connectingjoint 52 includes a first inner U-shaped tube 53 that communicates atits inlet end with the expansion chamber 43 of the manifold with aninterposed gasket 54 so as to provide sealing and also so as to permitsome flexibility in the connection. The first inner tube 53 is connectedto a megaphone tube 54 that extends into the expansion chamber 51 bymeans of a slip joint 55. There is a slight air gap between the ends ofthe inner pipe 53 and the megaphone tube 54 which forms a second innerpipe. An elastic inter connecting joint 56 encircles this slip joint andis held in place by means of a pair of hose clamps 57. As a result, someflexibility will be allowed between the inner pipe 53 and the megaphonetube 54 so as to permit expansion and contraction and also so as toabsorb vibrations.

A first outer pipe 58 encircles at least a portion of the length of thefirst inner pipe 53 and defines between these pipes a cooling jacket,indicated generally by the reference numeral 59. There are a pluralityof ribs 50 that extend integrally between the inner pipe 53 and theouter pipe 58 so as to provide a unitary construction and permit waterflow between the portions of the cooling jacket 59. A further elasticouter joint 61 encircles the remainder of the inner pipe 53, overliesthe elastic joint 56 and is affixed to a flange portion 62 which isfixed to an outer housing or jacket 63 of the second expansion chamber51 with the megaphone tube 54 by bolts, by a hose clamp 64. As a result,the cooling jacket 59 encircles the elastic joint 56. The other end ofthe outer joint 61 is held in place by a clamp 60.

It should be noted that the megaphone tube 54 is also formed with anouter portion 65 so as to form an extension of this cooling jacket intothe expansion chamber 51.

The second expansion chamber 51 has a vertically extending pipe portion66 formed at its outer end which communicates with a cooling jacket 67that encircles the expansion chamber 51 and which is formed by the outerhousing 63. An exhaust outlet pipe nipple 68 is formed in this outerjacket 63 and has slipped over it a flexible conduit 69 which deliversthe exhaust gases to a still further expansion chamber and watertrapdevice 71. This device 71 then discharges the exhaust gases through aconduit 72 to the tunnel 22 around the jet propulsion unit 18 fordischarge into the body water in which the watercraft is operating.

It should be noted that coolant from the engine may also be dischargedinto the exhaust manifold 43 in a suitable manner so as to provideadditional cooling and silencing.

Water is delivered to the cooling jacket 59 of the joint 52 by means ofa conduit 73 that communicates with a portion of the engine coolingjacket 41. This coolant will circulate around the joint 56 so as to coolit and then can enter into the megaphone section. In order to insurethat the joint 56 is fully encircled by coolant even during times whenthe engine is running slow and a low amount of water is circulated,there is a wall formed by the megaphone section 54 which has a dam likeeffect and which wall is indicated generally by the reference numeral74. This wall has a pair of upwardly positioned apertures 75 at theirupper peripheral edges so as to insure that the joint 56 will beencircled with cooling water at all times when the engine is running.This water can then flow through the apertures 75 to the jacket 67 so asto cool the second expansion chamber 51.

There is a still further dam formed around the discharged end of theexpansion chamber 51 by means of a gasket member 76 which gasket memberhas a pair of opening 77 at its upper end so as to provide the samedamming effect and trap water around the expansion chamber 51 even whenthe engine is running at slow speeds. As a result, it should be observedthat all critical components of the exhaust system will be completelysurrounded by water under all running conditions and this will insuregood cooling particularly of the elastic joints.

It is, of course, desirable that the water will be drained from thesecooling jackets when the engine is not running and the watercraft istaken out of the body of water in which it is operating. To this end,the gasket 76 is provided with a bleed opening 78 at its lower end whichwill let the water bleed out of this jacket and be discharged into theexhaust system through the nipple 68. In a like manner, the wall 74 isprovided with a bleed port 79 which will permit the water to bleed outin this same direction.

The gasket 54 (FIG. 5) between the joint 52 and the first expansionchamber 43 is also provided with a bleed port 81. In this way, when theengine is not running and the watercraft is out of the body of water inwhich it is operating, the cooling jacket 59 may drain through thisbleed port 81 and the conduit 49 for discharge.

The exhaust system and particularly the expansion chamber 51 is mountedfrom the engine by a construction best shown in FIGS. 8 and 9. There isprovided mounting bosses 82 on the outer jacket 63 that receive threadedfasteners 83 that pass through a mounting bracket 84. The mountingbracket 84 is affixed to the cylinder block 13 by means of threadedfasteners 85. In addition, threaded fasteners 86 also secure themounting bracket 84 to the cylinder head coverplate 38 for furtherrigidity.

It should be readily apparent from the foregoing description that thedescribed system provides a very effective exhaust system for a smallwatercraft and one in which the elastic joints are always well cooledand will, therefore, be protected from deterioration. Although anembodiment of the invention has been illustrated and described, variouschanges and modifications may be made without departing from the spiritand scope of the invention as defined by the appended claims.

We claim:
 1. A cooling system for the powering, water cooled, internalcombustion engine of a watercraft having a hull, said engine having acylinder block with a cooling jacket, an exhaust manifold for receivingexhaust gases from said engine with an exhaust manifold cooling jacketcompletely encircling said exhaust manifold and having an upper portionand a lower portion in open communication with said upper portion, anexhaust system for receiving exhaust gases from said exhaust manifoldand discharging said exhaust gases to the atmosphere, means for drawingcooling water from the body of water in which said watercraft isoperating and delivering such water only to said exhaust manifoldcooling jacket through the lower portion before circulation through saidcylinder block cooling jacket, means for delivery of at least a portionof such water from said exhaust manifold cooling jacket directly to saidcylinder block cooling jacket, and means for returning said coolingwater from said cylinder block cooling jacket to the body of waterthrough said exhaust system.
 2. A cooling system as set fourth in claimwherein the exhaust system is provided with an exhaust system coolingjacket and coolant is delivered to said exhaust system cooling jacketfrom said cylinder block cooling jacket.
 3. A cooling system as setfourth in claim 2 wherein the exhaust system is provided with a trapsection.
 4. A cooling system as set forth in claim 3 wherein the coolingwater from the exhaust system cooling jacket is returned to the exhaustsystem downstream of the trap section.
 5. A cooling system as set forthin claim 4 wherein coolant is returned to the body of water in which thewatercraft is operating from all of the cooling jackets through theexhaust system.
 6. A cooling system as set forth in claim 1 furtherincluding a jet propulsion unit drive by the engine for powering thewater craft.
 7. A cooling system as set forth in claim 6 wherein thecoolant for the engine is derived from the jet propulsion unit.
 8. Acooling system as set forth in claim 7 wherein the exhaust system isprovided with an exhaust system cooling jacket and coolant is deliveredto said exhaust system cooling jacket from the cylinder block coolingjacket.
 9. A cooling system as set forth in claim 8 wherein the exhaustsystem is provided with a trap section.
 10. A cooling system as setforth in claim 9 wherein the cooling water from the exhaust systemcooling jacket is returned to the exhaust system downstream of the trapsection.
 11. A cooling system as set forth in claim 10 wherein theexhaust system further includes an expansion chamber that is spaced fromthe engine within the hull of the watercraft and the exhaust gases andcooling water are delivered to said expansion chamber from the exhaustsystem.
 12. A cooling system as set forth in claim 1 wherein the meansfor delivering water from the exhaust manifold cooling jacket to thecylinder block cooling jacket includes restricted passage means.